Charleston, South Carolina: Hillary Clinton and Bernie Sanders jumped headlong into Sunday night's presidential debate by tangling over who's tougher on gun control and sketching sharply differing visions for the future of health care in America.

It was the last Democratic match-up before voting in the 2016 primary race begins in two weeks, with both sides intent on seizing the momentum.

Clinton rapped Sanders, the Vermont senator, for voting repeatedly with the National Rifle Association, and then welcomed his weekend reversal of position to support legislation that would deny gun manufacturers legal immunity.

Sanders, in turn, said Clinton's assertion that he kowtowed to the gun lobby was "disingenuous." On health care, Sanders released his plan for a government-run single-payer plan just hours before the debate, and used his opening statement to call for health care "for every man, woman and child as a right." Clinton, by contrast, urged less sweeping action to build on President Barack Obama's health care plan.

Health care should be a right of all people, not a privilege. This is not a radical idea. It exists in every other major country on earth.

The debate over gun control — an ongoing conflict between Clinton and Sanders — took on special import given the setting. The debate took plan just blocks from the Emanuel African Methodist Episcopal Church where nine parishioners were killed during Bible study last summer.

Gun control has emerged as a central theme in the race, with Clinton citing the issue as one of the major differences between the candidates.

On Saturday night, Sanders announced his support for legislation that would reverse a 2005 law he had supported that granted gun manufacturers legal immunity.

His changed position came in a statement after days of criticism from Clinton, who had attempted to use his previous vote to undercut his liberal image.

In an interview with Time magazine on Sunday, Sanders said that his plan would ultimately save taxpayers money by lowering their health care bills.

Sanders, meanwhile, has questioned Clinton's liberal credentials, casting the former secretary of state as a Wall Street ally who will switch her positions for political gain. But he's vowed to forgo negative attacks, a position that may be hard to maintain as the race intensifies.

Both candidates are competing for black voters in South Carolina, which hosts the fourth primary contest. At a party fundraising dinner Saturday night, they vowed to change criminal justice policies.

Former Maryland Gov. Martin O'Malley, who's been stuck in single digits since announcing his campaign last spring, also will be on the debate stage. The evening offers perhaps his last chance to improve his standing in the race.

The debate was sponsored by NBC, YouTube and the Congressional Black Caucus Institute.